Electron discharge device



Oct l7, 1944- I.A E. MouRoMTsEFF ET AL 2,360,707

ELECTRON DI SCHARGE DEVICE Filed Feb. 14, 1942 .t f4' Ameli/ua: if

Patented Oct. 17, 1944 ELECTRON DISCHARGE DEVICE Ilia E. Mouromtseff, Montclair,

and George M. Dinnick, Bloomfield, N. J., assignors to Westinghouse Electric & Manufacturing Gompany, East Pittsburgh, Pa., a corporation of Pennsylvania Application February 14, 1942, Serial No. 430,918

8 Claims.

This invention relates to electrical discharge devices and more particularly to such devices of the type employed in the radio iield and still more particularly to such devices employing anode and cathode electrodes, the surfaces of at least one of which are covered with relatively loose material presenting a roughened surface to the electrical forces passing thereto during operation of the device.

One of the objects of the present invention is to prevent disintegration of the roughened surfaces of the said electrodes.

Another object is to prevent electrostatic sparking on the said roughened surfaces of the said electrodes.

Still another object is to improve the stability and operating efficiency of electrical devices including anode and cathode electrodes the surface of at least-one of which is comprised of relatively loose material presenting a roughened surface to the electrical forces passing thereto during operation of the device.

Other objects and advantages will be apparent as the invention is more fully hereinafter disclosed.

In accordance with these objects we have discovered that the stability and operating efficiency of electron discharge devices of the general type known in the art as radio tubes which include anode and cathode electrodes at least one of which is surfaced with relatively loose material presenting a rough or uneven surface to the electrical discharges passing therebetween are markedly improved by use of the present invention. This improvement is accomplished by disposing in front of the said roughened or uneven surface an electrostatic shield member comprised of highly refractory metal, such as tungsten, tantalum and molybdenum. Said shield is provided with a plurality of' openings therein and is preferably highly foraminous for the substantially free and unobstructed passage of electrons therethrough and is electrically connected to the electrode over the surface of which it is disposed tobe at substantially the same electrical potential.

It is known that the electrostatic forces within an electricalV discharge -device between the anode and cathode electrodes tends to concentrate on the high spots of the electrode surfaces and we have found that where-the electrode surface consists of relatively loose particles of material the electrostatic forces during tube operation are suiicient to cause at least progressive dislodgement of the projecting particles of loose material and the carrying of the same to the .grid or opposite anode or cathode electrode sur- (graphite) also are particularly subject to the defect hereinabove described; and that devices incorporating both oxide coated cathodes and carbon or graphite surfaced anodes are more particularly subject to the defect hereinabove described.

As a specific embodiment of the present invention, but not as a limitation thereof, the adaptation of the same to an electrical discharge deivce incorporating an oxide coated cathode and a carbon or graphite anode will be described. Such a device is known in the art as a magnetron, high voltage transmitting tube,- or otherwise, according to its detail structure.

For further disclosure of the present invention reference should be made to the accompanying drawing wherein- Fig. 1 is a broken-away side elevational view of a typical electrode assembly of an electric discharge device adapted for use in the radio eld;

Fig. 2 is a sectional view of the same along plane 2-2 of Fig. 1;

Fig. 3 is a similar sectional view vention;

Fig. 4 is an enlarged fragmentary view illustrating the improved cathode .electrode of the present invention, and

Fig. 5 is an enlarged sectional view of the same.

The electric discharge device of the type illustrated customarily comprises an envelope (not shown) provided with a re-entrant stem I0 extending upwardly into said envelope and terminating in a press I in-whch are secured and through which extend a plurality of leading-in wires I2, I3 and I4 to the interior of the envelope, and on which is sustained an electrode assembly consisting of an oxide coated cathode C, a metallic grid G and anode A, which may be of carbon or graphite.

The electrode assembly and sustaining means iucstrating v the improved anode electrode of the present intherefor may be identified as comprising a flexible metallic band I5 wrapped around the stem ID below the press thereof and in rictional engagement therewith by means of the nut and bolt arrangement I6. At one side of said press are a plurality of standards I1 and I8 whichrare Welded to said band I5 and extend upwardly in said envelope. A corresponding pair of standards are secured to said band at the other side of said press. The standards I1 and I8 converge and are welded to each other at that portion where the standard I8 terminates. The standard I1 has the major portion thereof extending upwardly in said envelope and substantially parallel to the longitudinalv axis thereof an appreciable distance above the upward limit of the standard I8.

A cruciform spacer or insulator I9 having diametrically disposed openings in one of the cross arms thereof has the upper portion of the standardsI I1 extending through these openings, with the cross arm of the spacer I9 resting upon the. upper limit of the standards I8. The other cross arm of the Spacer I9 has a plurality of openings therein adapted to accommodate conductors and supports 20, 2|, 22 and 23. A suitably sized wire is helically wound and placed around the conductors 20, 23, and serves as the grid element G of the tube. An M-shaped filament C having its ends secured to the conductors 2l and 22 and having its upper bight portions secured to a pair of hooks serves as the cathode element. A small shallow carbon disc 24 having a circular opening therein is mounted on each of thev standards I1.

A rigid composite unitary anode A surrounds the grid G and cathode C. The anode A comprises an elongated hollow member consisting of two at sides 26 of sufficient width and arranged parallel to eachI other and integral with two curved portions 21 forming the other sides. A

cross sectional view of said anode A, at right angles to its major axis, is in the form of a rectangle having rounded ends' as indicated in Figs. 2 and 3. At the mid-width of each of said at sides and extending along the entire length thereof are outwardly extending lateral extensions 30. Each extension 30 is of appreciable cross-sectional area and has a longitudinally disposed opening 3| along the entire length thereof parallel to the longitudinal axis thereof.

The carbon or graphite anode A, which is a single element structure, per se; forms no part of the present invention except in combination with the electrostatic shield means of the present invention. It may be readilyformed bya machining operation or it may be` manufactured by extruding a suitable plastic of graphite and easily carbonizable binder after which extrusion step the plastic element may be red to complete carbonization and dryness as heretofore disclosed in the art. This composite unitary anode is composed essentially of graphite for good heat radiating properties which is one of the desirable features of an anode.

The anode A, as heretofore described, may be readily assembled on the assembly by merely sliding the standards, such as I1, through the longitudinally disposed openings 3| therein. The diameter of the openings 3l is substantially the same as that of the standards I1. A small shallow disc 24', the same type as the discs heretoiore described, has openings therein through which the upper portion of the standards l1 extend so that these discs rest upon the lateral extensions of the anode. A cruciform spacer or insulator32, similar t0 the spacer I9, also has openings therein adapted to accommodate the standards I1 which extend therethrough and project irpwardly therefrom.

The spacer 32 has openings adapted to accommodate the conductors 20 and 23 which extend therethrough. Short cross bars 33 are welded to the upper portion of the conductor 28 immediately adjacent and above the insulator 32, A cross bar is also welded to the lower p0rtion of the conductor 23 immediately adjacent and below the spacer I9. Hooks 29, which support the upper bights of the lament, have the shanks thereof integral with springs which rest in small recesses in the upper face of the insulator 32, with the shanks thereof extending through openings in said insulators.

Resting upon the insulator 32 and adjacent the outer portions thereof and welded to each of the standards I1 above the insulator is an inverted U-shaped rod 35 having the sides thereof welded to the standards I1 and I8 at the places where the sides of said U-shaped rods and standards intersect. A conductor 3E is electrically connected to one of the standards I1 and is hermetically sealed to a portion of the envelope other than the press and extends exteriorly of said envelope to form a terminal for the anode.

Cathode C is an oxide coated cathode and consists of either a round or flat electrically conducting metal base (b1) surfaced with a thermionically active coating (c), as indicated in Figs. 4 and 5, and in the present showing is IVI-shaped.

The improvement of the present invention consists in the provision of electrostatic shields SS disposed on opposite sides of grid electrode G and closely adjacent the facing surfaces of anode and cathode electrodes A and C respectively.

In accordance with the present invention, the relatively rough and uneven surfaces of each of the electrodes A and C are protected from the deleterious effect of the electrostatic forces within the device by electrostatic shieldsV S-S comprised of refractory metallic material, such as tungsten, tantalum and molybdenum. Electrostatic shields S-S may be helically wound coils, substantially as shown, or, alternatively, may consist of wire mesh material.

We have found that by providing electrostatic shields S-S in front of the rough surfaced anode and cathode electrodes the field lines of the electrostatic eld between vthe electrodes A and C concentrate thereon and prevent or inhibit the pulling olf of loose or projecting particles of material from the said anode and cathode surfaces and the migration of these loosened particles to the surface of the opposite electrode or to the surface of grid electrode G.

In any given adaptation the present invention employs an electrostatic shield consisting of a helically wound coil of refractory metal. The particular wire diameter and spacing between the coil turns may be varied widely without essential departure from the present invention and in general the spacing between the coil turns is relative to the electrostatic field normally present in the device. We have found that for most purposes the spacing between the wire turns should not exceed twice the diameter of the wire comprising the shield S and for most purposes a wire diameter of 2 to 10 mils is adequate for the present invention. As in most electrical discharge devices of the type hereinabove described the spacing between the cathode grid and anode electrodes is closely controlled, in general wehave found it preferable to employ relatively small wire diameter with a large number of coils turns per unit area.

In most instances we have found that it is sufcient for the purposes of the present invention to dispose the shields S-S in close contact with the anode and cathode surfaces substantially as illustrated. Where the electrostatic forces are relatively high, however, close spaced relationship of the shield to the electrode surface is preferred with one end of the shield electrically connected to the anode or cathode so that the shield S-S will be of the same electric potential as the anode or cathode.

In electric discharge devices of the type illustrated wherein anode A is comprised of metal and cathode C is surfaced with thermionically active material such as an oxide coating, shield S next the anode may be dispensed with and only shield S next the cathode employed. In electric discharge devices of the type illustrated, wherein cathode C is comprised of thermionically active metal and anode A is surfaced with, or comprised of, carbon or graphite, shield S may be dispensed with and shield S only employed to protect the surface of anode A.

Having hereinabove described the present invention generalically and specically, and given one specific embodiment thereof, it is believed apparent that the same may be widely varied Without essential departure therefrom and all such modifications and departures are contemplated as may fall within the scope of the following claims.

We claim:

1. An electric discharge device including spaced anode and cathode electrodes the surface of one of which electrodes is covered in part with loose and outwardly projecting particles of material subject to being removed therefrom by the electrostatic forces between the two said electrodes, means to prevent the removal of said particles of material, said means comprising an electrostatic shield comprised of a refractory metallic material disposed in continuous contact throughout its length and exposed in front of the surface of,

and electrically connected to, the said electrode having the projecting particles, said electrostatic shield being non-emissive and projecting from said surface of said electrode having the projecting particles and thereby providing for the location on said electrostatic shield of the electrostatic lines of force in preference to the location.

of said lines of force on said electrode surface having the projecting particles, and said electrostatic shield providing for the passage therethrough of electrons to and from said electrode surface having the projecting particles.

2. An electric discharge device including spaced anode and cathode electrodes the surface of one of which electrodes is covered in part with loose and outwardly projecting particles of material subject to being removed therefrom by the electrostatic forces between the two said electrodes, means to prevent the removal of said particles of material, said means comprising an electrostatic shield comprised of a refractory nonemissive metallic material selected from the group of tungsten, tantalum and molybdenum disposed in continuous contact throughout its length against and exposed in greater part in front of said projecting particles and in front of the surface of, and electrically connected to, the said electrode having the projecting particles, said electrostatic shield being non-emissive and projecting from said surface of said electrode having the projecting particles and thereby providing for the location on said electrostatic shield of the electrostatic lines of force in preference to the location. of said lines of force on said electrode surface havingthe projecting particles, and said electrostatic shield providing for the passage therethrough of electrons to and from said electrode surface having the projecting particles.

. 3. An electric discharge device including spaced anode and cathode electrodes the surface of one of which electrodes is covered in part with loose and outwardly projecting particles of material subject to being removed therefrom by the electrostatic forces between the two said electrodes, means to prevent the removal of said particles of material, said means comprising an electrostatic shield comprised of a helically wound wire coil having a coil-turn spacing and extending in contact for its full length with said electrode having the projecting particles, said coil being of highly refractory non-emissive metal and being electrically connected to said electrode having the projecting particles, said coil having its convolutions exposed in front of said electrode having the projecting particles and in front of said projecting particles, said coil providing for the location thereon of the electrostatic lines of force in front of said electrode surface having the projecting particles and in front of said particles in preference to the location of said lines of force on the said electrode surface having the projecting particles, and said coil providing for the passage between the convolutions thereof of electrons to and from said electrode surface having the projecting particles.

4. An electric discharge device comprising a cathode electrode, an anode electrode comprised of carbon, and an electrostatic shield member disposed in front of the anode electrode and in continuous contact for the entire length of the shield member .with the surface of the said anode, electrode and electrically connected therewith, said shield member consisting of a highly refractory' non-emissive metal and having a plurality of openings therethrough for the passage therethrough from one electrode surface to the other electrode surface.

5. An electric discharge device comprising a cathode electrode provided with an electron emissive surface consisting of relatively loosely adherent material and an electrostatic shield member substantially in its entirety overlying and exposed in front of and extending from end to end of the surface of said electron emissive surface and in contact therewith throughout the length of said shield member and electrically connected to the electrode, said shield member consisting of highly refractory non-emissive metal and having a plurality of openings therethrough for the free passage of electrons to and from the electrode surface. k

6. An electric discharge device having a thermionically active cathode, a grid electrode enclosing the cathode and an anode electrode having a surface consisting of carbon and graphite particles, said anode surrounding the said grid electrode, an electrostatic shield means disposed in front of and extending from end to end of the anode surface and in electrical contact with the said anode throughout the length of said shield means, said shield means having ya plurality of openings therethrough for the substantially free passage of electrons therethrough to the anode surface.

'7. An electric discharge device having a cathode surfaced lWith relatiwely loosely adherent thermionically emissive material, a grid electrode enclosing the cathode, and an anode electrode surrounding the said grid electrode, an electrostatic shield means disposed substantially in its entirety in front of and extending from end to end of the emissive surface of the cathode and in electrical contact at the under part only of the shield means With the said emissive surface of the cathode throughout the length of said shield means, said shield means providing openings therethrough for the substantially free passage of electrons from the emissive surface of the cathode to the said anode.

8. An electric discharge device having a thermionically active cathode, a grid electrode enclosing the cathode and an anode electrode surrounding the said grid electrode, the said anode and cathode surfaces each being covered with loosely adherent particles of material presenting a relatively uneven surface to the electrical discharge between the two electrodes, an electrostatic shield means disposed over the anode surface and in electrical contact with the said anode, and an electrostatic shield means disposed over the cathode surface and in electrical contact with the said cathode, each said shield means projecting substantially in its entirety in front of its respective electrode on which it is disposed and each said shield means being provided With openings therein for the substantially free passage of an electron current therethrough.

ILIA E. MOUROMTSEFF. GEORGE M. DINNICK. 

